An artificial valve (100) and related methods are provided for implantation in a patient's blood vessel (200), in particular an artificial heart valve, including a first (10) and a second (20) valve member each having a first smooth surface (11, 21) facing each other so as to form a sealing contact between the first and second valve members and further having at least one blood flow passage (13, 23a) extending from the first surface to a second surface (12, 22) located on an opposite side of the respective valve member, wherein at least one (10) of the valve members is arranged so as to be displaceable relative to the other (20) valve member in a slidable manner such that the passage (23a) of the second valve (20) member can be brought into at least partial alignment with the passage (13) of the first valve member (10) while maintaining the sealing contact between the first and second valve members, and a displacing mechanism (M; 50-56) for the relative displacement of the valve members (10, 20). The valve members can be made from ceramics. A valve system comprises the artificial valve (100) and additional components such as a motor (M), an energy source (E), a control unit (C), a pressure sensor (P), a feed back system and/or an alarm system.